1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a gate-in-panel (GIP) type dual gate structure liquid crystal display device for minimizing a region occupied by a gate driving unit in the GIP structure liquid crystal display device in which the gate driving unit supplying a gate driving signal is formed on a liquid crystal panel to implement a narrow-bezel, and improving image quality deterioration due to signal delay.
2. Description of the Related Art
In recent years, cathode ray tubes or the like in the related art have been replaced by flat display devices in the electronic information display device field, and such flat display devices may include a liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED), an organic light emitting diode (OLED), and the like. Liquid crystal display devices among such flat display devices have been mostly used now due to reasons such as mass production technologies, facilitation of a driving means, implementation of a high-quality screen, and embodiment of a large-sized area screen.
In particular, an active matrix type liquid crystal display device in which a thin-film transistor is used for a switching element is adequate to display dynamic images. A typical liquid crystal display device is provided a gate driving unit for generating and providing scan signals, and also provided with a data driving unit for providing data signals for displaying image gradation.
In particular, an active matrix liquid crystal display device in which a thin-film transistor is used for a switching element is adequate to display dynamic images.
FIG. 1 is a block diagram illustrating a basic configuration of a liquid crystal display device in the related art.
As illustrated in the drawing, a liquid crystal display device in the related art may include a liquid crystal panel 1 for displaying images and driving units 4, 5.
For the liquid crystal panel 1, a plurality of gate lines (GLs) and a plurality of data lines (DLs) are crossed with each other in a matrix form on a substrate using a glass to define a plurality of pixels at the crossed locations and images are displayed based on data signals applied to the pixels. The liquid crystal panel 1 may be divided into a active area (NA) formed with pixels to implement an image, and a non-active area (N/A) surrounding the active area (NA).
The driving units 4, 5 may include a gate driving unit 4 and a data driving unit 5. The gate driving unit 4 controls the turn on/off of switching elements in the pixels arranged on the liquid crystal panel 1 in response to a gate control signal (GCS) supplied from the timing controller (not shown). The gate driving unit 4 outputs a gate driving voltage (VG) to the liquid crystal panel 1 through the gate lines (GLs) to turn on a switching element of the pixel for each line progressively, thereby supplying a data signal supplied from the data driving unit 5 to the pixel for each horizontal period.
The data driving unit 5 modulates digital waveform image data into an analog waveform data signal in response to a data control signal (DCS) supplied from the timing controller. Next, a data signal corresponding to one horizontal period is simultaneously supplied to the liquid crystal panel 1 through all data lines (DLs) for each horizontal period, thereby allowing each pixel to display image gradation.
In such a liquid crystal display device having the foregoing structure, the structure of the gate driving unit 4 is relatively simple compared to that of the data driving unit 5, and a gate-in-panel (GIP) scheme in which the gate driving unit is fabricated on the non-active area (N/A) in the form of a thin-film transistor during the fabrication of a liquid crystal panel substrate, without using a scheme in which the gate driving unit is implemented as a separate integrated circuit (IC) and bonded to the liquid crystal panel has been proposed to reduce the volume, weight and fabrication cost of the liquid crystal display device.
Furthermore, the liquid crystal display device has a motion blur characteristic in which image quality is deteriorated due to the limitation of the liquid crystal response speed. In order to overcome the problem, there has been proposed a scheme in which a driving frequency above 120 Hz other than 60 Hz is applied to the liquid crystal display device. However, when the liquid crystal display device is driven at above 120 Hz, one horizontal period (1H) is reduced to that extent, thereby causing difficulty in securing a time for turning on switching elements for each pixel.
Accordingly, as illustrated in FIG. 1, a structure in which GIP type gate driving units 4 are embedded therein at the left and right sides of the liquid crystal panel 10, and an overlap interval between each front and rear gate driving voltage is provided to turn on the switching element through pre-charging has been applied to a recent liquid crystal display device.
However, as described above, in case of the GIP scheme, the gate driving units 2a, 2b are mounted on the liquid crystal panel 1 through thin-film transistors, and thus the width of the non-active area (N/A) at the left and right sides of the liquid crystal panel is increased. An area (2×N1) occupied by the gate driving units 2a, 2b at both sides of the liquid crystal panel 1 is about 9.5 mm, and most of that area is used based on the size of thin-film transistor.
FIG. 2 is a view for explaining an area occupied by one of the GIP type gate driving units on a liquid crystal panel in the related art. As illustrated in the drawing, a first 4-phase GIP gate driving unit 4a may include a clock signal (CLK 1˜CLK 4) and start signal (Vst) routing region 21, a gate high voltage (VGH) and gate low voltage (VGL) routing region 22, a shift register region 23, a level shift region 24, and an output routing region 25.
According to the foregoing structure, one stage outputting a gate driving voltage (VG) in the first gate driving unit 2a has a width L1 in the vertical (a short side of the liquid crystal panel) direction and a width N1 in the horizontal (a long side of the liquid crystal panel) direction. Accordingly, in case of a dual gate structure, it occupies a region having a width 2×N1 in the horizontal direction.
In recent years, a narrow bezel structure for minimizing the width of non-active area (N/A) of the liquid crystal display device has been preferentially used, thereby causing a problem that the foregoing dual GIP scheme is not applicable to a narrow bezel type liquid crystal display device with less than 5.5 mm.